Crystallization and particle design

 

The research within crystallization is focused at kinetics of nucleation, crystal growth, and agglomeration in order to predict and control the particle size distribution and shape of crystalline particulate products for scale prevention, improved solid-liquid separation, CO2-capture in precipitating systems, and for nano-particle production. The crystallization group also investigates fundamental mechanisms in the early formation of solid particles as well as mechanisms for growth of polycrystalline particles.

 

Optimisation of Glycol Loop Design and Operation

The aim of the project is to develop a simulation tool for glycol loops in processing of natural gas. This necessitates a deep understanding of the precipitation and crystallisation behaviour of salts and scale-forming carbonates in ethylene glycol (MEG) and water mixtures. Kinetics of calcium carbonate precipitation in the glycol injection point off-shore and the crystallization and separation of salts in the on-shore glycol reclamation units will be the main research tasks. The project is in collaboration with Institute of Energy Technology, Norway (IFE) and financed by several international oil and gas companies and the Research Council of Norway (NFR). Glycol injection point off-shore and the crystallization and separation of salts in the on-shore glycol reclamation units will be the main research tasks. Studies performed in the crystallization group in 2008 have shown that the MEG significantly affects the precipitation of calcium carbonate by lowering the growth rate, promoting nucleation and by shifting the polymorphic composition. Kinetic expressions have been developed to be implemented into computer simulator for particle formation control within glycol loops.

 

Industrial Crystallization and Powder Technology

The goal of this project is to relate solid/liquid separation characteristics and resulting dry powder flow properties to the underlying growth and agglomeration phenomena. It involves studies of inorganic salts and pharmaceuticals, and the primary target for the activity at NTNU is to link the parameters in the crystallisation process to the subsequent filtration step by focusing on common mechanisms for these selected systems. The project is in collaboration with POSTEC at Tel-Tek and is financed by the Research Council of Norway (NFR) and Norwegian industry partners.

In 2008 we have investigated the effect of supersaturation and temperature on the particle design of pharmaceutical compounds. We have identified a general mechanism of crystal growth switching whereby the particle shape is dramatically altered. This is illustrated for the precipitation of sodium glutamate by switching from the well-known needle crystals of ¿-glutamic acid to spherical particles of the same polymorph. Filtration resistance measurements as well as powder flow properties measured by uniaxial testing has shown that these spherical particles are unwanted, and in some cases the conditions can be met to avoid their formation.

 

Investigations of spherulitic growth in solutions – a mechanism for polycrystalline particles.

During 2008 we have collected experimental proof for spherulitic growth from solutions in contrast to literature claims of nano-aggregation as responsible for the same type of particles. Spherulitic growth is usually associated with melt crystallization but our findings show that it is a general mechanism is solid material formation. The time-dependent evolution of spherulitic growth is shown for calcium carbonate in the figure below (the scale bar equals one micrometer) and work is in progress to prove the validity of this growth process for numerous crystalline compounds, irrespective of the chemical nature of the consituents.